!|ExecuteCalculator         |
|given|when         |then?  |
|30 4 |+            |34     |
|30 4 |-            |26     |
|5    |!            |120    |
|4 6  |*            |24     |
|8  2 |/            |4      |
|1    |-            |-1     |
|     |+            |0      |
|8  0 |/            |<error>|
|     |$%^unknown*&^|<error>|
